It’s 2:00:01 pm and the Fed has just announced it will hike rates by 25 bps while using very dovish language to convey that just like “tapering was not tightening” in 2013, so “tightening isn’t really tightening”, and unleashing a massive buying order.

So far so good. But the real question is what does this mean for post-kneejerk market dynamics, and the one most important variable of all: liquidity.

The all too crucial, and overdue, answer to this question will be delivered when the Fed releases its “implementation note” concurrently with the FOMC statement which should explain all the nuances of just how the Fed will adjust the IOER-Reverse Repo piping that will be crucial to pull of the rate hike in practice, something which has been stumping

Two weeks ago, we cited repo-market expert E.D. Skyrm who calculated that moving general collateral higher by 25bps would require the Fed draining up to $800 billion in liquidity: “In 2013 on my website, I calculated that QE2 moved Repo rates, on average, 2.7 basis points for every $100B in QE. So, one very rough estimate moved GC 8 basis points and the other 2.7 basis points per hundred billion. In order to move GC 25 basis points higher, in a very rough estimate, the Fed needs to drain between $310B and $800B in liquidity.”

That may be conservative.

According to Citigroup’s latest estimate, the liquidity drain could be substantially greater. Here is the take of Jabaz Mathai

There will be a separate document from the NY Fed with details around the operational aspects of the liftoff. Of primary interest will be the size of the overnight reverse repo facility that the Fed will put in place to pull short rates higher. We don’t think it will be unlimited, but a size large enough that will keep short rates from falling below the 25bp floor – and the size could be as high as $1tn.

Putting this liquidity drain in context, the entire QE2 injected “only” $600 billion in liquidity in the span of many months, suggesting that as of tomorrow, the Fed may drain as much as 166% of its entire second quantitative easing operation overnight.

Whether that liquidity is inert and can be easily released by banks, and more importantly, non-banks without resulting in any additional risk tremors is the first $640 billion question that the Fed is facing. The second, third and fourth? Assuming a linear relationship and another 3 rate hikes until the end of 2014, this means that by the time short term rates hit 1%, the Fed may have soaked up as much $4 trillion in liquidity. Here one thing is certain: a $1 trillion drain may not have a material impact when starting from a $2.6 trillion excess reserve base. $4 trillion, however, will leave a mark (the Fed’s entire balance sheet is $4.5 trillion) especially once the market starts to discount just how the rate hike plumbing takes place.